Fiber to the home (FTTH) is regarded as the end state of broadband wireline access networks as fiber offers virtually unlimited bandwidth. FTTH replaces currently used copper infrastructure (e.g., telephone wires, coaxial cable, etc.). Multiplexing is a method used in optical networks to utilize the large bandwidth of optics to their full extent. Multiplexing enable several virtual channels to be formed on a single fiber. Therefore, multiplexing several optic signals increases the connectivity and utilization of a network. Time division multiplexing (TDM) is a method used to multiplex several signals onto one fiber optic link. TDM multiplexes several signals by establishing different virtual channels using different time slots. Wavelength division multiplexing (WDM) multiplexes the signals by having different virtual channels using different wavelengths.
WDM systems include a multiplexer and a demultiplexer. The WDM multiplexer combines signals of different wavelengths at the transmission side, and the WDM demultiplexer separates signals of different wavelength s at the receiver side. Optical signal multiplexers and demultiplexers are mostly reciprocal devices which can be used to combine and separate signals depending on the input direction of the signals.